For underfloor air distribution (UFAD) systems, more rapid mixing of the supply air with ambient airis desirable for better thermal comfort, and swirling air diffusers are usually used. In order to rigorously simulate the flow characteristics of such diffusers, we used the multi-grid technique and validated it with experimental results. In this paper, the technique is used to compare the square diffuser and the swirling diffuser.
Previous work on an Underfloor Air Distribution (UFAD) system with a single heat source anda single cooling diffuser at floor level developed by Lin has been extended to study the effects of the vertical location of the heat source and of multiple cooling diffusers. This is an attempt to produce more realistic models of UFAD systems. Both experimental and theoretical modeling is described in this paper. In the experiments, a plume and fountains represent a heat source and cooling diffusers respectively.
The research was oriented to analyze better the ventilation systems, in terms of cost-to-quality ratio. The matter of the paper is that a ventilation system is designed to work in certain quality conditions, but every quality has its cost. This cost comprises investment, energy consumption and operation-maintenance expenditures.
This study presents a critical analysis of assessment of ventilation systems effectiveness in terms of contaminant removal. For this purpose, experimental measurements are carried in a room of an experimental house called MARIA. Various ventilation scenarios are handled. The ventilated room is also equipped with a pine wood floor which emits several Volatile Organic Compounds which are considered as air pollutants here. Thereafter, based on boundary conditions given by measurements, Computational Fluid Dynamics (CFD) simulations are performed.
A distribution of contaminants from floor covering, exhaled air and human bioeffluents was examined in a mock-up of a typical two-person office by means of tracer-gases. The distribution was studied with two types of air terminal device for personalized ventilation combined with displacement ventilation. The results show that the type of personalized ventilation and its use affects the distribution of contaminants to a great extent, as does the type and location of contaminant sources.
Air exhaled by occupants may carry infectious agents and be one way of transmitting respiratory diseases in rooms. The exposure of occupants to exhaled air was examined at two different throw heights of underfloor ventilation combined with two types of personalized ventilation by means of full-scale experiments. The concentration of exhaled air from one occupant was measured in air inhaled by another occupant who used or did not use personalized ventilation.
This study shows the possiblity of improving indoor air quality thanks to underfloor ventilation systems. The top-return configuration and the floor-return one are tested and compared to a traditional ceililng based mixing system.
The number of Underfloor air systems (UFAD) has incresed 40 % between 1995 and 2002, thanks to the benefits it offers : lower churn costs, improved IAQ, lower energy costs, potential to reduce floor-to-ceiling heights. But knowledge of how to apply the technology is not widespread.
Design phases, construction and commissioning phases of the UFAD project are presented along with a paragraph on the importance of educating building occupants on UFAD.
That addendum 62n modifies the ANSI/ASHRAE Standard 62 "Ventilation for Acceptable Indoor Air Quality, it contains an update to the minimum prescribed ventilation rates and includes ventilation airflow "additivity" for dilution of people-source and building source contaminants.
The paper presents the results of the analysis of the impact of various ventilation systems on indoor air quality and energy consumption, performed for a typical Polish elementary school that was built in 1970s. Simulations were made with the use of two computer codes: CONTAM W and ESP-r. A multizone model of the global capacity of 9464 m3 was performed. The model contained 17 classrooms and 10 additional rooms typical of such buildings.
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